FIELD OF THE INVENTION
The invention comprises processes for manufacturing metallic hollow bodies with structural bulges and the apparatus for accomplishing such processes by way of a high current loop.
The reshaping of metallic work pieces by means of a magnetic impulse produced by a magnetic field concentrator is known.
Recently, a tubular hollow body with a structural bulge has been used for the most advanced technical application purposes in heat exchangers. For instance, through the use of a structural bulge a heat exchanger tube will develope a stronger turbulence of the heat exchanger mediums resulting in an improved heat transfer.
The manufacture such tubular hollow bodies with structural bulges by means of mechanical arrangements is extremely labor-intensive and therefore costly. Also, the deformation of tubular metallic hollow bodies to form structural bulges by means of a magnetic field concentrator offers considerable technical difficulties, particularly if the manufactured work pieces is to have a proportionate high production precision.
The present invention solves the task of creating a process for manufacturing metallic hollow bodies with structural bulges in a simple way by means of successive magnetic impulses applied to a hollow body to create uniformly formed structural bulges without shaping the processed work pieces in the area outside the structural bulge. This process distinguishes itself particularly through the employment of a simple and robust apparatus designed to accomplish the process.
This task is essentially solved according to the invention with a process for manufacturing metallic hollow bodies with structural bulges in that the hollow body is shrunk through the use of a magnetic impulse with the desired structural bulge corresponding to the shape of a support core or formed by expansion following removal of the support core.
In an advantageous process using the simplest preferred form of the invention, structural bulges are formed in a furnished hollow tubular body which is expediently guided through the metal forming opening in a magnetic field concentrator in intermittent processing steps. A profiled support core at the end of a carrying bar projects into the interior of the hollow body so it is within the opening in the magnetic field concentrator. The tubular hollow body is pulled over the support core and through the field concentrator which generates a first magnetic impulse around the hollow body to produce a structural bulge. The form of the structural bulge is determined by the grooves in the support core which proceed preferably in the longitudinal direction parallel to the common longitudinal axis of support core and the opening in the magnetic field concentrator.
After generating a first encircling, ring-shaped arrangement of structural bulges, the hollow body is pulled over the support core and through the magnetic field concentrator and twisted around its axis in a work step so that following a further magnetic impulse, a further encirclement of structural bulges is produced around the hollow body. Further encirclements of structural bulges are formed form from time to time during a gradual drawing back of the hollow body and by the generation of magnetic impulses.